You should check any paperwork/emails you have from the dealer, especially the receipt you should have received when you handed over the deposit. Hopefully this will clarify whether or not this was a refundable deposit.

Ultimately a deposit is an agreement from both parties in the deal - you agree to buy the car and the dealer agrees not to sell it to anyone else. If it's not clear from the paperwork that the deposit is non-refundable, you could attempt to argue in court that the terms of the deposit were not made clear, but you may only have a slim chance of victory.